Due to the parasitic capacitances of the transformer and inductor in Dual Active Bridge (DAB) converters, ringing may happen in the transformer currents especially when the transformer turns ratio is high. This high frequency current ringing may lead to EMI issues. It is found in this paper that the inductor connected on the low voltage side rather than the high voltage side of a DAB converter can help to mitigate the current ringing. The impedance of the magnetic tank is modelled to analyze the current ringing. The analysis is verified on a 2.5 kW DAB prototype.@en

The transformer in the dual active bridge converter (DAB) is the key element which provides galvanic insulation and voltage conversion. The parasitic parameters, including winding capacitance, ac resistance, and leakage inductance, are the primary considerations in its winding design. Without proper consideration of those parameters could result in issues on current ringing, high power loss, and overheating. In this paper, a comprehensive study is devoted to those parameters. A winding design method is presented by taking all those parameters into consideration. Special attention is paid to the impact of displacement winding, which is quite often in the manufacture and especially in prototype design phase. Both the normal and displacement winding will be studied and compared, with analytical, simulation, and experimental methods. Through comparison, additional coefficients are introduced to the simple analytical equations so that they could also be applied for displacement windings. Several considerations are given to control those parameters within a reasonable range in the design and manufacture phase. Finally, the analysis and design method are verified by finite element method and the experimental results on a 120 kHz prototype, and can be extended to other high-frequency magnetic designs.@en